Ribbon feed mechanism

ABSTRACT

A ribbon feed mechanism for printing machines has a toothed wheel rigidly mounted on a drive shaft at an angle relative to a plane perpendicular to the drive shaft axis. The toothed wheel will penetrate layers of outer convolutions of a roll of film ribbon on a take-up spool at varying locations relative to the ribbon width for feeding the film ribbon with equal length increments more consistently.

BACKGROUND OF THE INVENTION

The present invention relates to a ribbon feed mechanism for printing machines and more particularly relates to a toothed wheel rigidly mounted on a drive shaft at an angle relative to a plane perpendicular to the axis of the drive shaft for improving ribbon feed consistency.

A known ribbon feed mechanism for printing machines has a toothed wheel rigidly mounted on a drive shaft in a plane perpendicular to the axis of the drive shaft. The toothed wheel penetrates the outer convolutions of a roll of film ribbon for feeding the film ribbon. This ribbon feed mechanism is disclosed in U.S. Pat. No. 2,127,812 issued on Aug. 23, 1938 and invented by William A. Gabrielson.

Another known ribbon feed mechanism for printing machines includes a ribbon cartridge which has supported therein a drive shaft, a toothed wheel rigidly mounted on the drive shaft in a plane perpendicular to the axis of the drive shaft and a roll of film ribbon. The toothed wheel penetrates the outer convolutions of the roll of film ribbon for feeding the film ribbon. This ribbon feed mechanism is disclosed in U.S. Pat. No. 4,337,001 issued on June 29, 1982, invented by Samuel D. Cappotto and has the same assignee as the present invention.

Each of these known ribbon feed mechanisms has a disadvantage in that having the toothed wheel mounted on the drive shaft in a plane perpendicular to the axis of the drive shaft causes the teeth of the toothed wheel to penetrate the outer convolutions of the roll of film ribbon in substantially the same location relative to the ribbon width. The teeth normally penetrate several layers of outer convolutions of the film ribbon. When the ribbon feed mechanism is operated during relatively high speed printing (over 20 characters per second), such as printers operated from a memory source, the teeth will penetrate the ribbon in some of the same holes several times, due to the holes forming a substantially straight line pattern, as the ribbon winds on to the take-up spool which causes elongation of the holes. When the holes become elongated, the teeth will not consistently feed the ribbon with equal length increments which causes some characters to overstrike on the ribbon. Over striking of characters on some types of commonly used film ribbons will cause characters to be only partially printed.

SUMMARY OF THE INVENTION

In the illustrated embodiment of the present invention, there is shown a ribbon feed mechanism in a ribbon cartridge which has a toothed wheel mounted on a drive shaft at angle relative to a plane perpendicular to the axis of the drive shaft. The toothed wheel will penetrate layers of outer convolutions of a roll of film ribbon on a take-up spool at varying locations relative to the ribbon width for feeding the film ribbon with equal length increments more consistently.

Accordingly, the object of this invention is to provide a ribbon feed mechanism with the capability of feeding film ribbon with equal length increments more consistently for high speed printers.

Other objects, features, and advantages of the invention will become more apparent from the following description, including appended claims and accompanying drawing.

BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a plan view of a ribbon feed mechanism in a ribbon cartridge including the toothed wheel made in accordance with the present invention.

FIG. 2 is an elevational view of the drive shaft and the roll of film ribbon showing the toothed wheel oriented at an angle relative to a plane perpendicular to the axis of the drive shaft.

FIG. 3 is a plan view of FIG. 2.

FIG. 4 is a view of a section of the film ribbon showing holes in the ribbon at varying locations relative to the ribbon width caused by the toothed wheel penetrating the outer convolutions of the roll of film ribbon.

FIG. 5 is an exploded perspective view of the drive shaft.

FIG. 6 is a schematic view of a power drive for incrementally rotating the drive shaft.

FIG. 7 is a view of a section of film ribbon showing a prior art embodiment with the hole pattern being in substantially a straight line.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, a ribbon feed mechanism 10 is mounted in a ribbon cartridge 12 for feeding a film ribbon 14. The ribbon cartridge 12 has a base plate 16 and an intermediate platform 18 spaced above the base plate 16. In the ribbon cartridge 12, the ribbon 14 is directed from a supply spool 20, around several ribbon guides 22, 24, 26 and 28 and on to a roll 30. The supply spool 20 is rotatably supported on the platform 18. The roll 30 is supported on a take-up spool 32 for rotation therewith. The take-up spool 32 is rotatably mounted on a post 34. The post 34 is integrally formed on an arm 36. The arm 36 is pivotably mounted on a post 38. The post 38 is integrally formed from the base plate 16. A spring 40 is connected at one end to a spring anchor 42 integrally formed from the base plate 16 and is connected at the other end to a spring anchor 44 extending from the arm 36. A drive shaft 46 is rotatably mounted on the base plate 16.

Referring to FIG. 2 and FIG. 5 the drive shaft 46 has a centrally located hub 48, an external gear 50 integrally formed with the hub 48 and located at the lower end thereof, and a post 52 integrally formed with the hub 48 and located at the upper end thereof. An upper surface 54 of the hub 48 is angled relative to a plane 56 which is perpendicular to an axis 58 of the drive shaft 46. A toothed wheel 60 is placed on the upper surface 54. A collar 62 having a central opening 64 is mounted and cemented on the post 52. The collar 62 has a lower surface 66 substantially parallel to the upper surface 54 of the hub 48 to attach the toothed wheel 60 on to the drive shaft 46 at an angle 68 relative to the plane 56. The angle 68 can be in the range of 3°-10°. The toothed wheel 60 is formed from sheet metal with relatively pointed teeth 70. Alternatively, the toothed wheel 60 can be integrally molded with the drive shaft 46 from a suitable plastic material. The collar 62 holds the toothed wheel 60 tightly against the hub 48 for rotation therewith. The spring 40 biases the arm 36 clockwise with sufficient force to cause the teeth 70 to penetrate outer convolutions 72 (FIG. 3) of the roll 30 of film ribbon 14. The teeth 70 penetrates two to twelve layers of outer convolution 72.

Referring to FIG. 6, a power drive 74 includes a gear 76 in mesh with the gear 50 on the drive shaft 46. A ribbon drive 78 is operatively connected to a shaft 80 for rotating the gear 76 at substantially equal increments. A power source 82 is operatively connected to the ribbon drive 78 for supplying the needed power to incrementally rotated the gear 76 and the drive shaft 46.

Each time the power source 82 is activated, generally by a printing operation, the ribbon drive 78 will incrementally rotate the shaft 80. The shaft 80 will rotate the gear 76 which, in turn, will rotate the gear 50 counterclockwise. The gear 50 will rotate the toothed wheel 60 counterclockwise. The teeth 70 will penetrate the outer convolutions 72 of the roll 30 for rotating the roll 30 clockwise. Since the toothed wheel 60 is rigidly mounted on the drive shaft 46 at an angle 68 relative to the plane 56, the teeth 70 will penetrate the film ribbon 14 at varying locations relative to the ribbon width 84, as shown in FIG. 4. As the toothed wheel 60 continues to rotate, the teeth 70 will form holes 86 in a sine wave pattern. With the holes 86 continuing in this pattern, the teeth 70 will continue to penetrate the film ribbon 14 at locations which have not been previously penetrated. When the teeth 70 continue to penetrate the film ribbon 14 at locations with no previous penetrations, the film ribbon will be more consistently feed with equal length increments.

This structure overcomes the disadvantage of the prior art (FIG. 7) by preventing the teeth from causing elongation of holes 90 which results from a toothed wheel penetrating a ribbon 92 at substantially the same location relative to the ribbon width 94.

The ribbon feed mechanism 10 is shown mounted in a ribbon cartridge 12. Alternatively, the same ribbon feed mechanism 10 may be mounted on a typewriter frame structure not associated with a ribbon cartridge, such as that shown in the Gabrielson U.S. Pat. No. 2,127,812 previously referred to, while providing the same advantage of the present invention. 

What is claimed is:
 1. A ribbon feed mechanism for printing machines, the ribbon feed mechanism incldes a base plate, a take-up spool rotatably mounted on the base plate, a roll of film ribbon supported on the take-up spool, the roll of film ribbon having a predetermined ribbon width and having outer convolutions, a drive shaft mounted on the base plate and incrementally rotated for feeding the film ribbon, the drive shaft having an axis of rotation, the ribbon feed mechanism comprising:a toothed wheel fixed on the drive shaft for rotatiion therewith, said toothed wheel comprising means for rotating the take-up spool in response to incremental rotation of the drive shaft, said toothed wheel comprising a generally circular disc with a plurality of teeth extending from the circumference of said disc, the teeth all being located in a first plane which is oriented at an angle of 3° to 10° with respect to a second plane perpendicular to the axis of said drive shaft, the angular mounting of said toothed wheel comprising means for causing the teeth on said toothed wheel to penetrate the outer convolutions of the film ribbon at varying locations relative to the predetermined ribbon width.
 2. A ribbon feed mechanism for printing machines, the ribbon feed mechanism includes a ribbon cartridge having a base plate, a take-up spool rotatably mounted on the base plate, a roll of film ribbon supported on the take-up spool, the roll of film ribbon having a predetermined ribbon width and having outer convolutions, a drive shaft mounted on the base plate and incrementally rotated for feeding the film ribbon, the drive shaft having an axis of rotation, the ribbon feed mechanism comprising:a toothed wheel fixed on the drive shaft for rotation therewith, said toothed wheel comprising means for rotating the take-up spool in response to incremental rotation of the drive shaft, said toothed wheel comprising a generally circular disc with a plurality of teeth extending from the circumference of said disc, the teeth all being located in a first plane which is oriented at an angle of 3° to 10° with respect to a second plane perpendicular to the axis of said drive shaft, the angular mounting of said toothed wheel comprising means for causing the teeth on said toothed wheel to penetrate the outer convolutions of the film ribbon at varying locations relative to the predetermined ribbon width.
 3. The ribbon feed mechanism as defined in claim 1 wherein said toothed wheel is formed from sheet metal.
 4. The ribbon feed mechanism as defined in claim 2 further comprising an arm pivotably mounted on the base plate, the take-up spool rotatably mounted on said arm, and a spring connected to said arm and to the base plate for biasing the outer convolutions of the film ribbon against said toothed wheel causing the teeth of said toothed wheel to penetrate the outer convolutions of the film ribbon for rotating the take-up spool in response to the incremental rotation of the drive shaft. 